If you plan on carrying passengers back there you might want to consider significantly strengthening the area as well as adding structure for seat belts...and even a more extensive cage.

I agree with Jeffery P. Need to add more than just a seat. A roll bar would need to be attached to the frame. A bar attached to the seats is just cosmetic. I would go with restraints over belts, if it can be done. They were never made to carry humans safely back there.

Although my pup loves it back there.

Be Big,
AMAC

If heads of people sitting on the buggy's rear parcel shelf protrude higher than the roll bar, forget it.